Method of and apparatus for crystallization



March 4, 1930. E. w. KOPK E METHOD OF AND APPARATUS FOR CRYSTALLIZATIOILFiled Jan. 19, 1927 IN V EN TOR.

r m 4 m I Patented Mar. 4, 1930- UNITED STATES PATENT OFFICE EBN ST W.KOPKE, OF NEW YORK, N. Y., ASSIGNOR T0 FRANK L. ALLEN, 0F MONTCLAIR, NEWJERSEY METHOD OE AND APPARATUS FOR CRYSTALLIZATION Application filedJanuary 19, 1927. Serial No. 161,981.

improved apparatus for developing sugar v crystals from low grademassecuites or final massecuites in raw sugar factories, and ischaracterized by a simple and efi'ective method. of, and means forabstracting heat from the massecuite mass undergoing treatment as thecrystallizatlon of its sugar content proceeds.

In the preferred practical mode of carrying out the invention, I employcrystallizing apparatus of the usual type comprising a horizontallydisposed tank and a massecuite agitator therein comprising ahorizontally disposed shaft with arms distributed along its length sothat the different arms travel in vertical planes spread regularly apartfrom one end of the tank to the other. In adapt ing this type ofcrystallizer for use in carrying out the present invention, I providemeans for cooling the massecuite mass along vertical planes alternatingwith the planes of movement of the agitating arms. In the preferredconstruction employed by me, the cooling means for each plane comprisesone or more pipe convolutions or cooling coils mounted in the tankbetween each adjacent set of agitating arms. I associate with thedifierent cooling coils means for passing a cooling fluid, as water,therethrough so as to secure the desired cooling effect.

With sucha massecuite cooling and agitating system as described, I havefound it possible to subject the entire mass of the massecuite to acomparatively uniform cooling efiect, and have found that by suitablyregulatingsuch cooling efiect I may very materially shorten the periodrequired for crystallizing each charge of massecuite withv outreduction, but on the contrary, in some cases with an increase in thequantity of crystals recovered. In the practical use of the invention ithas been found that the decrease in the crystallization periodobtainable is ordinarily great enough to make the capacity of thecrystallizer'practically double that of the same crystallizer when notsubjected to the cooling effect characterizing the present invention,and in some instances the use of the invention has practically tripledthe efl'ective capacity of the crystallizer. Furthermore, it has beenfound that by the use of the invention the same ultimate exhaustion ofsugar crystals from the massecuite can be obtained with lessconcentration of the latter in the boiling pans preparatory tocrystallization. The fact that the invention permitsof lessconcentration of the massecuite treated is desirable not only because ofthe increased capacity and decreased cost of operation of the vacuumpans, but also because the reduction of the period of time to which themassecuite is exposed to high temperature tends of itself to increasethe quantity and improve the quality of the sugar crystals recoveredfrom the massecuite.

The "arious features of novelty which characterize my invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,however, its advantages and specific objects attained with its use,reference should be had to the accompanying drawings and descriptivematter in which I have illustrated and described preferred modes ofcarrying out the invention.

Of the drawings:

Fig. 1 is a sectional elevation on the line 1-1 of Fig. 2;

Fig. 2 is a transverse section on the line 2-2 of Fig. 1; and

Fig. 3 is a transverse section taken similarly .to Fig. 2, illustratinga modified con- 85 struction.

In Figs. 1 and 2 of the drawings, 1 indicates a metal tank which may bedescribed as generally rectangular in transverse section but having arounded bottom, and which 90 is provided adjacent one end with adischarge outlet 2. Axially mounted in the tank is a horizontal agitatorshaft 3 journalled in the the latter is rotated. The planes of movementof adjacent sets of stirrer arms are separated from one-another by adistance of two feet or so. As shown, the arms of the adjacent sets arestaggered in the sense that the arms of each set are at right angles tothe arms of the other set. In so far as described, the crystallizershown in Figs. 1 and 2 is of a type which is well known and in extensiveuse, though it may be noted that it has heretofore been customary-toconnect the outer tips of the stirrer arms of the diiferent sets byspiral ribbon-like members which are omitted in the construction shown.

For the purpose of the present invention, I have combined with the oldelements of the crystallizer shown in Figs. 1 and 2 the cooling coils 5.As shown, each cooling coil 5 is in the form of a pipe bent to formparallel horizontal limbs connected by return bends and disposed atregular spaced apart levels from the top to the bottom of the tank, thelengths of the difiierent limbs being such that each extends at its endsnearly to, but not into contact with the side walls of the tank. Asshown, each coil is in-efi'ect divided into an upper section above theshaft 3 and a lower section below that shaft, these two sections beingconnected by a nipple 8. As shown, the convolutions of each cooling coilare. mechanically supported by vertical supports 11 in the form of splitbars clamped on the pipe convolutions and resting at theirlower ends onthe bottom wall of the tank.

As shown also, each cooling coil receives a suitable cooling fluid,ordinarily water, at one end from a supply pipe 6 and discharges at itsother end into a drain pipe or gutter 7 which carries the dischargedwater to waste, or to a cooling tower or reservoir according toplantrequirements. As shown, cooling liquid is supplied from the pipe 6 tothe lower end of the coil convolutions through a coil end portion 5extending upward within the tank and passing out of the tank at its top,and connected above the tank with the pipe 6 through an individualthrottle or control valve 10. The discharge end 5" of each coil alsopasses out of the tank at the top of the latter and terminates in agoose neck portion discharging into the gutter 7 which, as shown, isarranged alongside the tank. The aggregate amount of cooling fluidsupplied to the different cooling coils 5 may be regulated by a throttlevalve 9 in the pipe 6 at the inlet side of its connections to the coils5.

With a suitable cooling liquid supply temperature and pressure and suchadjustment of the valves 9 and 10 as may be required, it is possible tohave each cooling coil exert any desired massecuite'cooling eflect. Thedistribution of the coil cooling efiects over planes alternating withthe planes of rotation of the stirrer arms 4 permits, in practice,

of substantial uniformity in the cooling effects exerted on differentportions of the massecuite. In consequence of the uniformity with whichthe massecuite is cooled, heat may be desirably extracted from themassecuite, particularly in the initial portion of the crystallizationprocess, at a rate much more rapid. than has heretofore been possiblewithout risk of overly rapid local cooling which, in the case of ahighly saturated massecuite, presents a certain danger of forming afalse or microscopic grain.

By the use of the invention, it is possible to have the crystallizationprocess proceed continuously and without interruption throughout theentire crystallization period, and there need be no more interruptionsin the formation of crystals as are now experienced as a result of thefact that after a certain comparatively rapid crystallization occurringwhile the massecuite is at one temperature, crystallization practicallyceases for a period of hours or even days during which the massecuiteslowly cools down to a lower temperature at which crystallization againproceeds at a relatively rapid rate. Such interruptions in thecrystallization process in practice result in a less thorough exhaustionof crystals from the mother liquor than is possible when thecrystallization process is continuous, as is made possible by theremoval of excess heat as provided for by the present invention,particularly when the excess heat is removed within a relatively shorttime after the massecuite is initially dropped from the vacuum pans intothe crystallizer.

It will be readily apparent to those skilled in the art that the use ofthe invention is not restricted to the form of the apparatus shown inFigs. 1 and 2 of the drawings, and one of the practical advantages ofthe invention is the ease with which massecuite cooling provisionsarranged and operated in accordance with the present invention may bereadily. added at a relatively low cost to existing crystallizers ofvarious forms and shapes with the result of greatly increasing theircapacity and improving their operation. For example, with a crystallizercomprising a cylindrical tank 1 as shown in Fig. 3, I may advantageouslydivide each cooling coil into two or more separate sections, each coilsection having its ends extending through the tank wall at convenientpoints. As-shown in Fig. 3, the-upper section 5A of each coil receivescooling liquid from a supply pipe 6A through a corresponding valve 10,and each lower coil section 5B receives cooling liquid at its lower endfrom another supply pipe QB through the corresponding individual controlvalve 10. The upper ends of all the coil sections discharge into acommon outlet trough 7.

I am aware of various arrangements heretofore proposed, and some ofwhich have gone into limited use, for cooling the massecuite bycirculating cooling water through pas-. sages in the stirrer, and bymeans of pipes extending into the crystallizer tank, but in noneof'these prior constructions, so far as I am aware, has there been suchuniformity in or control of the cooling action as is contemplated andprovided for with my invention. In'particular, none of the priorarrangements known to me is adapted to secure the rapid reduction oftemperature in the massecuite when the latter is first received in thecrystallizer from the vacuum pans which may be secured by the use of thepresent in-' vention and without danger of an obj ectionable formationof false or microscopic grain or other impairment of the product recov-7 in planes alternating with the first mentioned planes, said coolingaction being distributed in each of the first mentioned planessubstantially entirely across the massecuite.

2. A sugar crystalizer comprising a tank, a

stirring device mounted in said tank and comprising a shaft and stirringarms secured to the shaft at intervals along the length of the latter,and cooling coils disposed in said tank and adapted to subject themassecuite in the tank to a cooling effect distributed over planesalternating with" the planes of movement of the stirring arms andextending substantially entirely across the tank, and means forregulating the relative cooling effects produced in the differentplanes.

3. A sugar crystalizer comprising a tank, a

- stirring device mounted in said tank and comprising a shaft andstirring arms secured to the shaft at intervals along the length of thelatter, and cooling coils disposed in said tank and adapted to subjectthe massecuite in the tank to a cooling effect distributed over planesalternating with the planes of movement of the stirring arms andextending substantially entirely across the tank, and means forregulating the relative cooling effects in different portions of thedifierent planes.

4. The method of treating massecuites which consists in establishing aplurality of ,similar' temperature modifying effects in a series ofplanes, and passing the massecuites through substantially the entirearea of said planes, to produce a uniform temperature modification ofthe entire mass.

5. The method of treating massecuites passing the massecuitecontinuously and un- 1 interruptedly through substantially the entirearea of said planes, to produce a uniform temperature modification ofthe entire mass.

6. A. massecuite treating apparatus comprising a tank, pipe coilsdisposed in said tank across the same in a plurality of spaced planes,means for supplying a temperature modifying fluid agent at substantiallythe same temperature to all of said coils, and means for uninterruptedlypassing the massecuite through said planes of coils througlr out theirentire area to thereby uniformly modify the temperature of the entiremass.

Signed at New York city, in the county of New York, and State of NewYork, this 14th day of January, A. D. 1927.

ERNST lV. KOPKE.

